Aspects of the invention can relate to a projector for displaying images on a projection surface such as a screen, and specifically, to a technology of performing automatic focus adjustment.
Related art automatic focus adjustment technology for projectors, for example, can include a technology of repeating imaging of test patterns displayed on a projection surface, such as a screen and performing frequency analysis of shot images while moving the focal point and focusing it on a position where the largest amount of high frequency components are contained within the shot images. In this related art technology, the processing time increases in the case of performing frequency analysis with software, while the cost increases in the case of performing frequency analysis using dedicated hardware.
Further, in order to speed up the processing and suppress the cost, related art automatic focus adjustment technology can use contrast differences between light and dark points within a shot image to focus a focal point on a position where the contrast difference becomes largest. See, for example, Japanese Patent Application Publication No. Hei-8-292496. Further, a similar automatic focus adjustment technology can use sum of squares of brightness differences between adjacent pixels within the shot image in place of the contrast differences. See, for example, Japanese Patent Application Publication No. Hei-6-3577. Japanese Patent Application Publication No. 2000-241874 is also an example of related art.